1. Field of the Invention
The present invention relates generally to a diffuser, and more specifically to an exhaust axial flow diffuser for a gas turbine engine.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a turbomachine, such as a compressor or a turbine or a gas turbine engine, a diffuser is used in several locations to improve the airflow either into or out of a turbomachine. Inlet diffusers are used to slow down the airflow entering a compressor. Outlet diffusers are used to limit backflow pressure and therefore improve the flow exiting the turbomachine. An industrial gas turbine engine makes use of an axial flow diffuser at the exit of the engine to improve the performance of the engine. The exhaust from the turbine enters the exhaust diffuser and therefore is hot gas flow. A typical exhaust diffuser in an IGT includes a plurality of struts extending between the outer shroud and the inner shroud that forms the diffuser flow path. In an IGT—which is a large and heavy engine—these struts can be quite thick compared to other turbomachine airfoils. In the exhaust flow of the diffuser, a wake is formed behind each of the struts due to flow separation that will lower the performance of the engine.
Prior art diffuser struts for a large diffuser have thick struts with a standard blunt trailing edge shape as seen in FIG. 1. This type of strut can reduce the incident angle losses. The losses behind this blunt trailing edge strut are excessive. Another prior art diffuser has cross sectional shapes of an airfoil which includes a trailing edge that tapers down to a point as seen in FIG. 2. This improves the airflow around the strut to limit vortices from developing that reduce the efficiency by increasing the backflow pressure. One problem with the tear drop shaped prior art strut of FIG. 2 is a shorter life for the strut. The strut is exposed to the hot exhaust gas flow exiting the engine. The sharp edge of this trailing edge shaped strut will be affected by erosion or corrosion much more than would a blunt trailing edge of FIG. 1.